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Scientists are studying Zika to see if Canadian mosquitoes can spread the virus

A Brock University lab is using samples of the virus to see if Canadian mosquitoes can potentially transmit Zika humans.

Fiona Hunter feeds the mosquitoes at her lab at Brock University. Her lab is researching if the Zika virus can be spread by native Canadian mosquitoes. (Marcus Oleniuk / Toronto Star) | Order this photo

On Friday morning, medical entomologist Fiona Hunter rolled up her sleeve, stuck her arm inside a glass box, and casually offered up her veins for a feeding frenzy.

The box is home to a colony of Aedes aegypti mosquitoes, which Hunter and her laboratory employees are prone to feeding with their own blood. Her secure, temperature-controlled insectary at Brock University is one of the few places in Canada where the tropical mosquito can live. This week, the lab became home to another exotic resident: the Zika virus.

Zika is primarily spread by the A. aegypti mosquito in countries with hot, humid climates. While Hunter says Canadians won’t be seeing homegrown A. aegypti anytime soon, she wants to investigate whether other mosquito species can transmit the virus — specifically, species that live in Ontario.

As the Zika epidemic has spread across the Americas, public health officials have emphasized the virus is unlikely to establish itself in countries like Canada, where the Zika-spreading A. aegypti species cannot survive.

But Hunter doesn’t like to assume. “Never say never,” said Hunter, whose insectary lab opened in 2012 and previously focused on West Nile virus. “Never say we’re safe.”

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Since Brazil confirmed its first Zika cases in early 2015, the virus has spread to nearly 30 countries and territories across Central America, South America, Mexico and the Caribbean.

Earlier this month, the World Health Organization declared a public health emergency over Zika’s potential link to a surge in neurological disorders, primarily Guillain-Barré syndrome, an autoimmune disorder, and microcephaly, a birth defect associated with abnormally small heads and developmental issues.

Because Zika was previously assumed to only cause mild disease, few researchers have studied the virus over the last 50 years. The current epidemic, however, has triggered a flurry of scientific interest.

From Hunter’s point of view, she’d rather understand Zika’s potential in Canada — before the virus ever has a chance of spreading here.

According to Hunter, Ontario has 67 mosquito species, about five of which have appeared in the last decade. About “a dozen species” already here could be potential vectors, or disease carriers, of the Zika virus, she says.

The plan is to infect them all and see whether the virus can travel through the mosquito’s body to replicate in its salivary glands, Hunter says.

One candidate is the Aedes japonicus mosquito, an invasive species Hunter first detected in 2001 in Niagara — the southern-dwelling mosquito’s “gateway to Canada,” according to Hunter. Today, A. japonicus is the fifth-most common mosquito she catches in her traps.

Hunter will also keep an eye out for the Aedes albopictus, a close relative of A. aegypti, which is also capable of transmitting Zika. The mosquito has been found as far north as New York state. In 2002, two turned up in one of Hunter’s traps, likely “blown north” from the U.S. (she hasn’t found them again).

The verdict’s out on whether A. albopictus could permanently move into Canada. Georgetown University researcher Peter Armbruster, who studies how mosquitoes overwinter, told the Star his research models show A. albopictus is unlikely to survive local winters and therefore “will not be able to establish in Toronto on a year-round basis.”

But Hunter notes Ontario winters are getting warmer and we could be seeing the A. albopictus “probably in the next decade.”

“It’s really a matter of time before it gets here,” she said.

In the context of stopping the current epidemic, the task of identifying other potential mosquito vectors currently ranks “very low” on the priority list, according to Dr. Pedro Alonso, a vector expert and director of the WHO’s malaria program. But he emphasized he would never discourage research by academic groups, especially if they have the funding to support it.

In Canada, Hunter’s lab was a natural contender for studying Zika in mosquitoes. The lab already had funding for research on vector-borne viruses. It is also the only Canadian facility, aside from the Public Health Agency of Canada’s Winnipeg lab, with a Level 3 containment lab that includes an insectary.

Hunter’s Zika strain, which she received from the PHAC Wednesday, is originally from Thailand. She said the PHAC is isolating a Brazilian strain from the current outbreak, which she also plans to study once it’s available.

“We can be proactive,” she said. “We don’t have to wait until some traveller comes back to Canada with Zika virus and gets bitten by local mosquitoes, and wait on tenterhooks to see whether or not there can be local transmission.”

Don’t panic over Ontario’s first Zika case

With Ontario’s first case of Zika now confirmed, health officials are stressing an important fact: do not panic.

It’s not unusual to see infections in returning travellers. Many countries have already reported “imported” cases of Zika, including Canada, which previously confirmed cases in British Columbia, Alberta and Quebec.

Ontario’s chief medical officer, Dr. David Williams, also stressed that the risk to Ontarians is “very low.” The two mosquito species known to transmit Zika — A. aegyptiand A. albopictus — aren’t established in Canada. And while Zika can be transmitted through sexual intercourse, scientists believe these incidents are rare, with only two previously documented cases.

Canadian Blood Services has also recently implemented new rules, banning blood donation from individuals who have travelled outside of Canada, continental United States or Europe within the last 21 days — a very conservative time period, as the Zika virus only remains in the blood for about a week.

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